Clyde Tombaugh discovered Pluto in 1930 at Lowell Observatory in Flagstaff. Here's how Pluto won - and lost - its planetary ...

In 2006, the International Astronomical Union (IAU) voted on the definition of a planet. Famously, Pluto no longer met the ...

Even many years later, some astronomers want to revise the definition of a planet to clarify the parameters that set planets apart from other celestial objects. But why isn't Pluto considered a ...

Pluto was reclassified from a planet to a dwarf planet by the International Astronomical Union because it did not meet all three criteria of their updated definition of a planet. According to the ...